In the drilling of deep wells in earth formations many different types of earth formations are encountered and boring or drilling operations in each of these types of formations require differing boring equipment. For example, in loose or unconsolidated earth formations such as gravel strata, it is desirable to utilize integral drill bits having a plurality of blades for cutting away the formation. Where consolidated, very hard earth strata is encountered, for example, in deep earth formations, it is typically desirable to employ drill bits having a plurality of rotary toothed cutters. The teeth of the rotary cutters are cooperatively associated so that the earth formation is cut away as the drill bit is rotated at the extremity of the drill pipe extending from the drilling rig to the formation being drilled. The typical rotary cutter type drill bit or "rock bit" includes a body portion from which depend three legs. Spindles or cutter supports extend inwardly toward the center line of the drill bit from each of these legs. Rotary cone type cutter elements having cutter teeth formed thereon are typically rotatably secured to each of the supports or spindles and are oriented in such manner that the cutter teeth thereon engage and cut away the earth formation as the bit structure is rotated by the drill pipe.
One of the paramount disadvantages of drill bits having rotary cutters is the inability of the cutter bearings to withstand the severe wear characteristics to which the drill bit is typically subjected. As drilling operations occur, rock bits are subjected to severe impacting and vibration as well as other wear inducing factors that are highly detrimental to the service life of the rotary cutter bearings and other components of such drill bits. At times, much of the weight of the drill pipe to which the rotary drill is connected may be caused to act upon the cutter, subjecting the cutters and their bearings to tremendous mechanical loads. It is therefore desirable that rotary drill devices be provided which incorporate bearings having the capability of withstanding extremely high forces, excessive vibration as well as high temperature operation.
Typically, the drill bodies of rotary cutter devices take the form of integral cast or forged structures that are very expensive to manufacture because of the complex configuration thereof. It is also desirable to provide a rotary drill bit construction having a body structure of exceptional strength and durability and yet being of relatively low cost. Drill bit cost is also adversely affected by the typical requirement for expensive materials for most of the structural components of such bits. For example, an expensive bearing quality material may be required for the drill cutters or the entire body structure of the bit if any part thereof is to define a wear resistant bearing surface.
It is therefore a primary feature of the present invention to provide a novel rotary cutter type drill bit construction that allows optimum utilization of materials for the various components thereof to insure optimum drilling capability and exceptional service life.
It is also a feature of the present invention to provide a novel rotary cutter type earth boring drill construction wherein a unique cutter supporting bearing and spindle assembly may be connected to structural components of the drill body by welding.
Among the several features of the present invention is contemplated the provision of a novel rotary earth boring drill construction incorporating bearing and spindle assemblies that, through optimum use of material, are capable of withstanding extremely severe operational loads.
It is an even further feature of the present invention to provide a novel rotary earth boring bit construction whereby the body structure of the bit may be formed by assembling a plurality of low cost body sections, thereby promoting the low cost aspects of the drill construction.
It is also an important feature of the present invention to provide a novel rotary earth boring bit construction whereby rotary cutter elements are assembled to respective spindle and bearing assemblies utilizing controlled changes in dimension by heating and cooling various ones of the drill bit components.
It is also a feature of the present invention to provide a novel rotary earth boring drill construction whereby mechanical locking means may be provided to insure positive locking of rotary cutter elements to the spindle bearings and thereby insure against separation of the cutter elements by vibration and other operationally induced forces.
It is a feature of the present invention to provide a method of manufacturing a rotary cutter type drill bit wherein cutter, bearing and spindle assemblies may be developed prior to attachment thereof to the drill body.
It is an even further feature of the present invention to provide a method of manufacturing a rotary cutter type drill bit wherein cutter, bearing and spindle assemblies may be assembled to body sections prior to connection of the body sections to form an integral body.
Other and further objects, advantages and features of the invention will become obvious to one skilled in the art upon an understanding of the illustrative embodiments about to be described and various advantages, not referred to herein, will occur to one skilled in the art upon employment of the invention in practice.